In 2005 he won the Monterey Sports Car Championships, the final race of the season in the ALMS. He was partnered by Tom Chilton in a Zytek 04S LMP1 sports prototype.

He also represented Japan in the A1 Grand Prix series for the first time at Eastern Creek in November 2005, and was lucky to escape with only a concussion after a spectacular crash in which the engine separated from the chassis. He also occurred in another spectacular crash at the A1 Grand Prix round in Mexico. The cars were under a yellow flag when as they were coming onto the pit straight Shimoda's car was launched airborne after hitting the back of A1 Team New Zealand's car. Shimoda escaped unhurt.